This project is concerned with analyzing the internal structure of the synaptic membranes in the retina and the membrane events which accompany transmitter release by the photoreceptor cell endings using electron microscopy of thin-sectioned specimens, ultrastructural tracer techniques and freeze-fracturing. BIBLIOGRAPHIC REFERENCES: Raviola, E., and N.B. Gilula. Intramembrane organization of specialized contacts in the outer plexiform layer of the retina. A freeze-fracture study in monkeys and rabbits. J. Cell Biol. 65: 192-222, 1975. Raviola, E., and G. Raviola. Difference in internal structure of the postsynaptic membrane at ribbon and conventional synapses in the inner plexiform layer of the retina. J. Cell Biol. 67: 355a, 1975.